1. Field of Invention
This invention relates in general to fuel injection systems for internal combustion engines and, in particular, to control systems responding with a gas sensor in the intake manifold to the air mixture containing EGR for controlling the amount of fuel injected into the system.
2. Prior Art
Most fuel management systems can be classified as either an open loop control or a closed loop control system. In the open loop control system, the fuel mixture is preprogrammed and the fuel management system responds only to certain engine operation parameters to alter the fuel mixture. In the closed loop control system, the fuel mixture is also preprogrammed with the fuel management system responding to certain engine operation parameters; however, with the use of an output sensor, the fuel management system is continuously updated to account for fuel management system tolerances, ambient conditions and for particular engine operating conditions so that the actual air/fuel ratio is substantially equal to the desired air/fuel ratio.
Typically most output sensors respond to the characteristics of the fuel mixture and are positioned in the exhaust system of the engine downstream from the point where all the exhaust gases are gathered. This position is generally necessary because most of the sensors are operated at elevated temperatures and the exhaust gases provide the heat source necessary to heat the sensor to its operating temperature. However, this position is a long "time" distance away from the source of the gas mixture and therefore the response time of the system to correct or update the fuel injection is slow. Additionally, the system response time is further altered according to the mode of operation of the engine as indicated by the flow rate of the exhaust gas.